Insulated glass units are commonly used in windows and doors because of their superior resistance to heat flow as compared to single glazed windows or doors. Their superior insulating qualities make insulated glass units useable for almost any application in which a structure is temperature controlled inside as compared to the outside.
Insulated glass units generally include at least two panes of glass having identical shapes. The two panes of glass are separated by an air gap and held together by a spacer which follows the exterior perimeter of the two panes of glass and is inset somewhat from the peripheral edges of the two panes of glass. The spacer is adhesively bonded to the two panes of glass and creates the, so called, primary seal between the two panes of glass. The space thus formed between the two panes of glass may be filled with ambient air or other gases to create a dead space which provides the insulating qualities of insulated glass units.
As discussed above, the spacer in an insulated glass unit is inset from the peripheral edges of the glass panes leading to a trough shaped space bounded on two sides by the glass panes and on one side by the spacer. In the manufacturing of insulating glass units, this space is filled with an adhesive sealant which forms the, so called, secondary seal of the insulated glass unit. The secondary seal may be applied using a variety of different adhesive sealants. These include time setting sealants, such as silicones or butyl rubber sealants. Sometimes two part sealants utilizing a resin and a catalyst to polymerize the resin are utilized. More commonly in modern manufacturing, hot melt adhesive sealants are used. Hot melt adhesive sealants are general applied in a liquid state at a temperature of approximately 350° F. and harden upon cooling to ambient temperature.
In high volume manufacturing facilities, the secondary seal is commonly applied by fully automated equipment in which a computer controlled robotic sealant applying head is moved around the peripheral edges of the insulated glass unit under computer control and applies the sealant to the edge or edges of the insulated glass unit. Fully automated secondary edge sealing equipment of this sort can apply to the secondary seal to very large numbers of insulating glass units in a production run. Typically, the insulated glass units in these circumstances are produced in large runs of identical units.
Fully automated edge sealing equipment of this type requires highly precise computer numerically controlled programming in order to apply a consistent edge seal. Because of this and the requirement that the equipment be programmable to handle many different sizes and shapes of insulated glass units cause this sort of equipment to be quite expensive to purchase and maintain.
There also exist in the window and door manufacturing industry smaller manufacturing facilities at which short runs of custom made windows or doors are manufactured in small quantities or even in single unique units. In these facilities, secondary edge sealing is generally accomplished by hand held equipment in which an operator applies the secondary sealant with a device similar to a caulking gun. These hand held dispensing units may have power to assist to dispensing the sealant and some control over the dispensing rate that is automated. It is not possible to make as consistent quality edge seals with these devices as fully automated equipment and the operator must have considerable practice and skill in order to achieve a good result.
Accordingly, there is still room for improvement in the area of secondary edge sealing of insulated glass units.